Time-element electroresponsive device and system employing the same



June 3, 1930.

C. F. CARPENTER ET AL TIME ELEMENT ELECTRORESPNSIVE DEVICE AND SYSTEM EMPLOYING THE SAME Filed obi. 20, 1925 Fig.2..

n w 1 .m(w Opo gb W 2 n h MWmwT flO a m 2 2 L Ml w FL 2 m Patented June 3, 1930 UNITED STATES PATENT OFFICE CHARLES E. CARPENTER, OF SGHENECTADY, NEW YORK, AND DONALD I. BOHN, OF

BADIN, NORTH CAROLINA, ASSIGNORS PORATION OF NEW YORK TO GENERAL ELEQT'RIC COMPANY, A COR- TIME-ELEMENT ELECTRORESPONSIVE DEVICE AND SYSTEM EMPLOYING THE SAME Application filed October 20, 1955. Serial No.v 63,794.

The improvements provided by our present invention enable elcctro-responsive devices such as switches, relays, or the like, to respond to predetermined electrical conditions a time interval after the occurrence thereof. I y

In one of its aspects thelinvention provides an improved arrangement of controlling apparatus and circuits whereby anelectro-responsive switch may be operated at will under the controlof suitable. 'master switch mechanism to open and close a controlled circuit andals'o operated automatically to open the controlled circuit a time interval after the occurrence of predetermined electrical conditions, such as undervoltage or. failure of power.

The invention also provides an improved form of combined thermal and electro-mag- 'netic electro-responsive controlling device which operates instantaneously upon a pre-' determined 'energization thereof and responds; with a time delay to a reduction in the energization of the device. When energized responsively to the voltage of the 0 controlled circuit and arranged in accord ance with our invention, the improved time element controlling device cooperates with the master switch mechanism in controlling the energizing circuit of an electro-responsive line switch or contactor so as to afford time element undervoltage protection to a motor or other electrical apparatus. 7

A betterunderstanding ofthe invention may be had by referenceto thefaccompanying drawings which illustrate a time element circuit controlling device' embodying a preferred form of the invention and I adapted to control the circuit of'an alternat- 40 ing .current electric motor, although it shouldbe understood that the inventionis not necessarily restricted to alternating current service. i

Fig. 1 is a perspective view of our improved time element electro-responsive' device arranged for alternating current service and Fig. 2 is-a circuit diagram showing an alternating current motor control system arranged to provide automatic time element undervoltage protection in accordance with the invention and embodying the form of time element controlling device illustrated in Fig. 1.

As shown 'in Fig, 1 the electro-responsive controlling device is arranged to close a controlled circuit substantially instantane-- ously upon the energization of the device and to maintain the controlled circuit closed for a time interval after a reduction in theenergization of the device, although it will be obvious to those skilled in the art that the device may be readily modified to the time element circuit closing type if desired. v \e The time delay in the operation of the device is-obtained by means of the thermal element 10 which is of the'bimetallic type and is suitably secured at one end to an insulating base or support 11 and carries at to mechanically move the thermal element 10 into the circuit closing position upon energization of the operating winding 15. It will be seen that the armature 17 is pivotally mounted upon the-pin 18 so as to be biased into the position in'which it is held by the stop 19 as shown in Fig. 1. The operating arm 20, which is carried by the armature 17, is arranged to engage with the free, end ofthermal element 10 when the armature 17 a is moved to the attracted position, thereby mechanically moving; the thermalv element 10 so as to engage the contact 12 with the stationary contact 13.

The thermal element 10 isarranged to be heated whenever the operating winding 15 of the electromagnet is energized. When applied to alternating current service this may be accomplished by arranging the auxv iliary winding 21 in inductive relation with m viously the thermal element may be heated in other ways in either alternating current or direct current services, if desired, as b means of suitable heated coils.

From the foregoing it will be evident that when the winding is energized with a suitable alternating current, the armature 17 is i attracted and carries the operating arm 20 into engagement with the thermal element 10 to move the contact 12 into engagement with the contact 13. As the energization or] winding .15 continues the thermal element 10 is heated by the current induced in the auxiliary winding 21. After a predetermined time interval the temperature of the thermal element 10 reaches the value required to cause the element 10 to flex sufliciently to maintain the contact 12 in engagement with the contact 13 independently of the armature 17L Hence, if the energization of winding 15 is reduced sufliciently to permit the armaturel'l to return to the biased position, the thermal element 10 maintains the contact, 12 in engagement with the statlionary contact 13 for the time interval required for the thermal element to cool.

In case the winding 15 is reenergized before the thermal element 10 is cooled it will ing 15..

, previously described.

be evident that the circuit controlled by the contacts 12 and 13 is maintained closed during the period of deenergization of the wind- If, however, the element 10 is cooled sufiiciently to disengage the contact 12 from the contact 13, the circuit controlled thereby is opened and is reclosed upon the reenergization of winding 15 in the manner The time element electro-responsive device shown in Fig. 1 is particularly adapted for use in an automatic undervoltage motor protective system such as shown in Fig. 2. In this system the circuit through w h'rclhthe three phase alternating current motor 22 re ceives power from suitable lines 23 .is controlled by an electr'o-responsive switch 24; which is biased to the open position as shown- 'The operating winding of switch 24 is energized from separate supply lines such as the direct current supply lines25 under the control of the motor starting push button 26 and motor stopping push button 27 although the-switch 24 may be energized directly from the main supply lines 23 if desired, also other forms of master switch mechanism may be provided for establishing contactor 24. The arrangement is such' that when the contact 12 carried at the free end of thermal element 10 is in engagement with the contact 13, the energization and deenergi zation of the operating winding of line switch 24 is under the control respectively of the starting push button 26 and the stop- .ping push button 27. When the line contactor 24 is closed to establish the running connections for the motor 22 and the voltage ofthe supply lines 23 is decreased for any reason below the'value at which operation of the motor 22 may be continued safely, the time element device 28 is designed to automatically interrupt the energizing circuit of the line contactor 24: after a desired time interval to thereby disconnect the motor 22 from the supply lines 23.

With the arrangement of the automatic undervoltage protective device as shown, the operating winding 15 is energized at all times in accordance with the voltage of the supply lines 23 when the controlled switch 29 is closed. Consequently, when the voltage of the supply lines is at a suitable operating value the armature 17 is maintained in the attracted position and the thermal element 10 is mechanically operated to and held in the circuit closing position. At the same time, the thermal element 10 is heated winding 21. Under these conditions closure of the starting push .button 26 establishes an energizing circuit for the line contactor 24 extending from the upper supply line 25 through the stop push button 27, the start- I ing push button 26, theoperating winding of. line contactor 2t, the thermal element 10, contacts 12and 13, thence to the lower sup ply-line 25. Upon the resulting closure of the'line contactor, the motor 22 is connected for operation from the supply lines 23 and a holdingcircuit in shunt with the starting push button 26 is closed by the auxiliary contact 29 with which the line contactor 24 is provided. Thus, the contactor 24:1's maintained energized independently of the starting push button 26 and the interruption of theenergizingcircuit of the contactor is under the control of either the stop push but; ton or the automatic time element electroresponsive device 28.

The heated-thermal element 10 of the device 28 functions to maintain theenergizing circuit of contactor 24 closed for a time incondition or failure of power occurs.

' in case'the undervoltage or failure of power sufiicient to cause the contactor 24-to is only temporary, the energizing circuit of line switch 24 is maintained closed until the return of normal voltage conditions. If the undervoltage or failure of power persists for an extended interval, the thermal element 10 then is permitted to cool sufliciently to separatethe contacts 12 and 13 and interrupt the energizing circuit of the -line conta'ctor; When the line contactor 24 is energized from' a separate source as shown, the motor 22 remainsconnected'to the supply lines 23 during the temporary undervoltage condition. When, on the other hand, the

line contactor 24 is energized directly from the supply lines 23, the undervoltage may be drop open., However, upon the return of normal voltage before the thermal element 10 cools the contactor 24 is immediately reclosed to reconnect the motor 22 to supply line 23. Upon the return of normal voltage conditions the thermal responsive element 10 is substantially instantaneously operated to the circuit closing position upon the attraction of armature 17, but the motor 22 is not connected to the supply lines- 23" .until after operation of the start'push button 26 as previously described.

While we have described the invention in connection with an alternating current system, it will be evident that the invention may be applied with equal advantage to atford automatic undervoltage protection to direct current circuits.

What we claim as new and desire to secure by Letters Patent of the United States is 1. A time element circuit controlling device including a movable switch member, electro-res'ponsive means for moving the member from one circuit controlling position to a second circuit controlling position,

'electro-responsive means for moving thev member to a second circuit controlling position, and thermal responsive means arranged to be heated in accordance with the energization'of said electroresponsive means for malntaming the'swltch member in said secondposition for a timeinterval while the 3. A time element electro-responsive circuit controlling device including cooperating switch contacts biased out of engagement, a movable thermal element for maintaining the contacts in engagement when the element is heated, electro-responsive means for moving the said contacts into engagement upon a predetermined energization o and means for heating said element in accordance with the energization of said electroresponsive means to maintain the said contacts in engagement during the cooling of the thermal element after a reduction in the energization of said electro-responsive means.

4. A time element electro-responsive circuit controlling device including a. movable switch element, a movable thermal responsive element mechanically connected to control the movement of said switch element from a predetermined position, and electroresponsive means connected to be energized responsively to an electrical characteristic for mechanicallymoving the said switch element to said predetermined position when the said electrical characteristic is above a predetermined value and for heating the thermal responsive element to cause the same said means,

to retain the switch element in said position the element to move the contact with a time,

delay from a predetermined circuit controlling po'sition upon the cooling of the thermal element due to variation in the said characteristic below a predetermined value, and electro-responsive means energized responsively to said characteristic for substantially instantaneouslyoperating the said movable contact to said position'when the electrical characteristic is increased to said predetermined value.

6. An electro-responsive time" elementcircuit controlling device including a movable thermal responsive. circuit controlling element heated in accordance with an electrical characteristic and having a contact mounted thereupon and adapted to assume a predetermined circuit controlling position when said characteristic is at a predeter= mined value, electro-responsive means energized responsively to said variable electrical characteristic and having a movable member for substantially instantaneously operating the said movable element to move the contact to said position upon an increase of said variable electrical characteristic to said predetermined value, said movable member being'arranged to move to an inactive position upon a reduction in the value of said electrical characteristic to permit the thermal responsive element to retain the contact in said circuit controlling position for a time interval during the cooling of the thermal element after the reduction in the value of said electrical characteristic.

7. A time element electro-responsive cir-' cuit controlling device including a thermal responsive circuit controlling element having a contact mounted therefrom, means for heating the element in accordance with an electrical characteristic to cause the same to move the contact with a time delay action from one circuit controlling position to a second circuit controlling position when the said electrical characteristic is reduced below a predetermined value, electro-responsive means energized in accordance with the value of said electrical characteristic and having a movable member biased to an inactive position and arranged to substantially instantaneously move said thermal element to carry said contact to the said first position when the electrical characteristic is at said predetermined value and return to said inactive position upon a reduction in the value of the electrical characteristic to permit the'movable thermal element to maintainthe contact in'said first circuit controlling position a time interval thereafter during the cooling of the thermal element.

8. A time element circuit controlling de- J vice including a thermal responsive circuit controlling element operable into engage-- ment with a cooperating contact, an electromagnet having a movable magnetic member mechanically connected "to move the thermal element into engagement with the cooperating contact upon a predetermined energization of the electro-magnet, and means inductively associated with the electro-magnet for heating the thermal element in accordance with the energization thereof to maintain the element in engagement with the cooperating contact for a time interval magnetic member for mechanically operat-,

after a reduction in the energizationof the e'lectro-magn'et.

9. A time element undervoltage relay including a movable thermal responsive circuit controlling element biased out of engagement-with a cooperating contact when the thermal element is at normal temperature, an electro-magnet having a movable ing the thermal circuit controlling element into engagement with the cooperating contact upon-energization of the electro-magnet above a predeterminedwoltage, and a wind ing disposed in inductive relation with the operating winding oi the electro-magnet and arranged to heat the thermal respons ve element to cause the same to remain in engagement with the cooperating contact for a time interval after the reduction in the energizing voltage of the electro-magnet.

10-. A time element under-voltage circuit protective system including an electroresponsive switch for controlling the circuit,

said switch being biased for operation" to the circuit-interrupting position, master switch mechanism for controlling the energizing connections of said switch to close and open the circuit at will, and automatic electroresponsive time element means connected to be eneregized in accordance with the voltage of the circuit and having normally open circuit-controlling means electrically operated to the closed position and connected to cooperate with said master switch to establish energizing connectionsfor said electroresponsive switch when the voltage of the circuit is above a predetermined value and operable with a time delay independently of said master switch mechanism to interrupt the energizing connections of the electroresponsive switch an interval after a re- "duction in the voltage of the circuit below a predetermined value.

11. A time element under-voltage circuit protective system including an electroresponsive switch for controlling the circuit, said switch being biased to the circuit-interrupting position, a normally open control switch operable to the closed position to establish a circuit for energizing the said electroresponsive switch for operation thereof to the closed position, and automatic time element electroresponsive means energized in accordance with the voltage of the controlled circuit and having circuit controlling means biased to the open position and electrically operated to the closed position to maintain the energizing circuit "of thesaid electroresponsive switch estabto the closed positio n, a second electroresponsive means connected to be energized in accordance with the voltage of the circuit controlled by said first switch, normally open circuit-controlling means operated by said second means to the closed position and electrically connected to maintain'the energizing circuit of said first electroresponsive means. established independently. of said normally open switch, and time delay means for preventing operation of said circuit controlling means from the closed position for p a. time interval after a reduction in the volta e of the circuit controlled b said first switc below a predetermined va ue.

1o 13. A time element under-voltage circuit protective system including an electrore- 'sponsive' circuitecontrolling switch biased to the circuit-interrupting position,'a normally open switch for connecting said electrore- 'sponsive switch. to beenergized-fpr operahim to the'circuit-closing position, an electroresponsive circuit-controlling device biased to thecircuit-opening position and con- 7 nectedto. be energized in accordance with the voltage of the circuit controlledby the first switch for operation-to the closed posi I tion, time delay means associated with said device to be rendered efiective upon operation thereof to the closed position for delaying operation thereof in accordance with 1 its bias, and connections jointly controlled by said device and said electroresponsive" switch through which. the said electrores onsive switch'is maintained energized inependently of'the normally open switch for atime interval after a redetermined reduction in the voltage pf t e1;circuit controlled by e electroresponsive switch.

In witne -whereof CHARLES F. CARPEN- TEIthaS hereunto set his handthis 10th day of October, 1925, and DONALD I. BoHN' has hereunto set hisxhand this 12th day of October,1925. I v CHARLES F. CARPENTER; ii; DONALD I. BOHN. j 

